1. Field of the Invention
The present invention relates to an electron tube having a linear member, such as, for example, a cathode filament, a wire grid, a wire damper for the cathode filament or for the wire grid, and a wire spacer for the cathode filament or the wire grid. More particularly, the present invention relates to a fixing structure of the linear member in a fluorescent luminous tube, such as, a fluorescent display tube in which the linear member is mounted within the display tube under tension.
2. Description of the Prior Art
A fluorescent display tube, as an example of a conventional electron tube, will be described with reference to FIGS. 9(a) and 9(b). FIG. 9(a) is a cross-sectional view illustrating a fluorescent display tube taken along the line X2—X2 of FIG. 9(b) looking in the direction of the arrow. FIG. 9(b) is a cross-sectional view illustrating a fluorescent display tube taken along the line X1—X1 of FIG. 9(a) looking in the direction of the arrow.
The fluorescent display tube has a hermetic container formed of substrates 111 and 112 to be opposite to each other, and side plates 121 to 124. The hermetic container contains cathode filaments 23, grids 43, and anode electrodes 31 on which a fluorescent material 32 is deposited. The fluorescent material 32 gives forth fluorescence by electrons emitted from the filament 2. The grid 43 controls electrons emitted from the filament 23.
A pair of aluminum (Al) thin films 211 and 212 for use in a cathode electrode are formed on the substrate 111. One end of the filament 23 is held between the Al thin film 211 and an aluminum (Al) wire 251, while the other end of the filament is held between the Al thin film 212 and an aluminum (Al) wire 252. Both the ends of the filament 23 are welded to the Al thin films 211 and 212, respectively, together with the Al wires 251 and 252 by an ultrasonic bonding. Spacers 261 and 262 sustain the filaments 23 in a predetermined height.
In addition, a pair of aluminum (Al) thin films 611 and 612 for fixing a damper 63 are formed on the substrate 111. One end of the damper 63 is held between the Al thin film 611 and an Al wire 621 while the other end of the damper 63 is held between the Al thin film 612 and an Al wire 622. Both the ends of the wire damper 63 are bonded to the Al thin films 611 and 612, respectively, together with the Al wires 621 and 622 by the ultrasonic bonding. Spacers 641 and 642 sustain the wire damper 63 in a predetermined height. The wire damper 63, as shown in FIG. 9(b), is spaced away from the filament 23 as being in no contact with the filament 23. When the filament 23 vibrates, the wire damper 63 touches with the filament 23 for preventing the filament 23 from contacting with other electrodes. The fluorescent display tube shown in FIG. 9 is disclosed in Japanese Patent Laid-open Publication No. 2002-245925.
The conventional fluorescent display tube shown in FIG. 9, requires to dispose therein the filament having one end fixed between the Al thin film 211 and the Al wire 251 and the other end fixed between the Al thin film 212 and the Al wire 252, as well as the spacers 261 and 262 for sustaining filaments in a predetermined elevated level. This results in increasing dead space in the fluorescent display tube, which is obstructive to reduce size of the fluorescent display tube. The dead space further increases if the wire dampers are disposed in the fluorescent display tube as shown in FIG. 9. The dead space still further increases if the liner members, such as, wired grids, or wire spacers for the filaments, are disposed in the fluorescent display tube.